Oxygen Sensor (O

The exhaust oxygen sensor or O
2
S is mounted in the exhaust stream where it monitors oxygen content in the exhaust gas. The newer models have a heated oxygen sensor, which is slightly different from the conventional sensor. The oxygen content in the exhaust is a measure of the air/fuel mixture going into the engine. The oxygen in the exhaust reacts with the oxygen sensor to produce a voltage which is read by the ECM/PCM. The voltage output is very low, ranging from 0.1 volt in a high oxygen-lean mixture condition to 0.9 volt in a low oxygen-rich mixture condition.

Testing the oxygen sensor without the use of special scan tools to observe its operation is difficult. The oxygen sensor should not be condemned because of Codes 44, 45, or 131-134. These codes tell you the oxygen sensor is seeing a constant rich or leak mixture. This code is usually not due to a bad oxygen sensor. A rich mixture could be a dirty air filter, stuck choke, leaking injector, burn valve or other problems. A lean mixture could be a vacuum leak, low fuel pressure or even a bad spark plug wire. Follow the proper charts to test the components.

PRECAUTIONS

Careful handling of the oxygen sensor is essential.

The electrical pigtail and connector are permanently attached and should not be removed from the oxygen sensor.

The in-line electrical connector and louvered end of the oxygen sensor must be kept free of grease, dirt and other contaminants.

Avoid using cleaning solvents of any type on the oxygen sensor.

Do not drop or roughly handle the oxygen sensor.

The oxygen sensor may be difficult to remove if the engine temperature is below 120°F (48°C). Excessive force may damage the threads in the exhaust manifold or exhaust pipe.

REMOVAL and INSTALLATION

See Figure 1

The oxygen sensor must be replaced every 30,000 miles (48,309 km). The sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive removal force may damage the threads in the exhaust manifold or pipe and result in injury; follow the removal procedure carefully.

Locate the oxygen sensor; it protrudes from the center of the exhaust manifold at the front of the engine compartment. (The sensor looks somewhat like a spark plug.)

Fig. Fig. 1: The oxygen sensor protrudes from the center of the exhaust manifold at the front of the engine compartment and looks somewhat like a spark plug

Disengage the electrical connector from the oxygen sensor.

Spray a commercial heat riser solvent onto the sensor threads and allow it to soak in for at least five minutes.

Carefully
unscrew and remove the sensor.

To install:

Coat the new sensor's threads with GM anti-seize compound No. 5613695 or the equivalent. This is not a conventional anti-seize paste. The use of a regular compound may electrically insulate the sensor, rendering it inoperative. You must coat the threads with an electrically conductive anti-seize compound.

Tighten the sensor to 30 ft. lbs. (42 Nm). Do not overtighten.

Attach the electrical connector. Be careful not to damage the electrical pigtail. Check the sensor boot for proper fit and installation.